During a surgical procedure the timely acquisition of ultrasound imagery can mean the difference between life and death for the patient. Many devices and techniques have been developed or suggested to facilitate the speedy acquisition of ultrasound data, including laparoscopic ultrasound probes, finger mounted probes and hand-held probes having the ability to wirelessly transmit image data. Unfortunately, a number of problems continue to hamper medical personnel in the use of these devices.
For a hand held probe, users must take an extra mental step to remember and account for the distance between the position of the sensor head and the position of the user's hand. Frequently, the user is required to perform many mental tasks simultaneously, such as reviewing imagery; manipulating the probe to effect delicate changes in the probe pressure and angle; and accessing a bank of medical knowledge in an effort to diagnose a medical problem. During the stress of a medical procedure the task of mentally calculating the probe position and orientation, based on knowledge of the probe geometry, is an extra task that taxes the already highly-taxed mental resources of the medical professional. In addition, the extra displacement of the hand from the target probe head position reduces the ability to utilize muscle memory for probe positioning.
Another problem is the disassociation, both in time and location, of the tactile input that a medical professional receives from his fingers, during a procedure, and the ultrasound imagery data. For example, for situations in which a medical procedure must be interrupted for imaging to occur, it may be quite difficult for the surgeon to match the tactile information that he notes with the imagery previously acquired. In diagnostic procedures, it may be impossible for the medical professional to gain both tactile information and image information simultaneously. The task of remembering and piecing together the two types of data presents an additional challenge to the medical professional.
Yet another problem encountered by users of currently available probes is the difficulty in fitting a probe into a small area. The human body is largely composed of delicate tissue, and the object of the medical professional is often to address a localized medical problem while disturbing surrounding or intervening tissue as little as possible. For example, one type of desired imagery that is currently very difficult to acquire is imagery from the posterior of the heart. Hand held probes and/or probes having a large cross-section present a particular difficulty when it is desirable to move the probe head through body tissue in order to obtain imagery of interest.
Still another issue presented by currently available probes is the awkwardness of use, as the probe is typically tethered by a multi-conductor coaxial cable that is one to three meters long, to an imaging station. It is typically difficult to twist this cable, so rotating the probe about its longitudinal axis may prove difficult. In addition, the heavy weight of the cable and need to grip the probe handle have the potential to create repetitive motion injuries to sonographers and physicians who use the ultrasound probe.
Moreover, many of the tools available for imaging the internal regions of the human body may be unavailable in a particular case, due to special conditions. For example, although trans-esophageal imaging is an extremely valuable tool for cardiac surgeons, there are instances in which the esophagus is diseased, making it potentially harmful to insert a probe into the esophagus. In these situations, having some other method of imaging would be invaluable.
A problem faced specifically by cardiothoracic surgeons is that of assessing plaque deposits in a portion of the aortic arch and ascending aorta prior to accessing the portion of the aorta. If there are plaque deposits in the part of the aorta accessed, the deposit or a portion of it may break off, travel through the blood stream and lodge in a blood vessel, causing great damage to tissue that is dependent on the vessel for its blood supply. Although Doppler ultrasound probes are currently used for the assessment of plaque deposits in the aortic arch and ascending aorta, currently available intra-operative probes are about 10 cm long and rigid, for accessing interior portions of the body. Although this is potentially useful in some situations, it greatly complicates the task of successfully placing the probe for imaging a blood vessel and as in so many other intra-operative situations, permitting the user to maintain a correct sense for the orientation and position of the probe transducer.
Another issue faced by cardiothoracic surgeons is that of finding coronary arteries in a difficult-to-assess patient. Although in many patients the coronary arteries run close to or on the surface of the heart, in perhaps 10% of patients one or more coronary arteries are buried in cardiac tissue. This can create a serious problem for a cardiothoracic surgeon attempting to perform a bypass operation, in finding the correct artery. In a few unfortunate cases, an artery has been misidentified, leading to negative surgical results.
Moreover, the current configuration consisting of a permanently attached probe connected to a cable presents sterility issues. The cable typically could be autoclaved, but the sensor is too delicate. The entire sensor and cable assembly, however, is rather bulky for fitting into a bath of disinfecting liquid and the connector is typically not designed to be immersed in disinfectant. As a result, achieving satisfactory sterility of the probe and cable assembly can present a challenge to hospital personnel.
Moreover, changing the command to the sensor head, for example increasing or decreasing power, or changing the field of view of the scan or the frequency transmitted for typical current systems requires an adjustment at the imaging station, which is awkward for a medical professional in the middle of a procedure.
Although finger-mounted probes are currently known, they are typically either bulky and inflexible or they do not form precise imagery.